The invention relates to a gaming machine comprising a reel of which a circumferential surface is divided in a number of fields which each bear a symbol from several symbols, which may include a blank, drive means for rotating the reel, memory means for storing data representing allowed rotational stop positions of the reel where the reel is allowed to stop, the number of allowed stop positions being greater than said number of fields, random number generator means for randomly generating an address of a location of said memory means containing data representing an allowed stop position and stop means for controlling the drive means to stop rotation of the reel opposite a winning line at a rotational stop position which corresponds to said randomly generated memory means address.
U.S. Pat. No. 4,711,451 discloses three types of prior art gaming machines, i.e. a standard gaming machine, a multiple stop gaming machine and a virtual reel gaming machine.
A standard gaming machine typically employs reels which have one stop position for each symbol (or indicia) on the reel, each stop position having one random number associated with it. To stop a reel in a standard gaming machine, a random number is generated and the reel stopped at the stop position associated with the random number.
A multiple stop gaming machine employs reels having multiple stop positions for many of the symbols on the reel and fewer to one stop position for higher paying symbols. Each stop position has only one random number associated with it. To stop the reel a random number is generated and the reel is stopped at the stop position associated with the random number. Because of the different numbers of stop positions for the symbols the odds of winning can be differentiated.
A virtual reel gaming machine employs reels typically having one stop position associated with each symbol and a number of stop positions have multiple random numbers associated with them. A gaming machine of this type is disclosed by U.S. Pat. No. 4,448,419.
With all said prior art machines a random number is generated and the associated reel is stopped at the stop position associated with the generated random number.
The gaming machine proposed by U.S. Pat. No. 4,711,451 includes a number of rotating symbol bearing reels, each reel having several stop positions associated with each symbol on the reel. A specially designed reel mapping scheme allows one standard reel stop control software routine to control the stopping of the reels when the machine is operated as standard gaming machine, multiple stop gaming machine or a virtual reel gaming machine. According to said document, to provide gaming machines to play one out of a standard type game, multiple stop type game or virtual reel type game, gaming machine manufacturers had to develop different reel stop controls including different software routines for each game type, while the software development for the different types of games was considered extremely costly. Therefore, to reduce costs, the machine with selectable play type using one standard reel stop control software routine was proposed.
With the combined gaming machine disclosed by U.S. Pat. No. 4,711,451, for a plurality of reels of the machine a single software routine is used for each of the reels in turn. To make it possible to have the combined machine operate in accordance with one of said prior art individual machines, the combined machine comprises three memory arrays, i.e. a mapping index array, a reel stop map and a single reel map. To have the combined machine to operate according to a multiple stop gaming machine locations of the mapping index array contain a sequence of offset values of indexes referring to physical reel stop positions where the reel is allowed to stop. Said memory locations containing indexes for allowed reel stop positions form a sequence of memory locations without intermediate memory locations of unallowed stop positions. With a sequence of k allowed stop positions a random generator has a random number range of 0-(k-1), each referring to a respective memory location of the mapping index array containing said indexes. After having generated a random number the index of the memory location addressed by the random number is read. From the read out index addresses are calculated for a memory location of each of the reel stop map and the symbol reel map. An addressed memory location of the reel stop map contains stop position data for driving means where the reel must stop. An addressed location of the symbol reel map contains symbol data of a specific symbol from P+1 different symbols.
To have the combined gaming machine operated as a standard gaming machine or a virtual gaming machine the contents of the mapping index array must be altered and by doing so the addressing schemes for the reel stop map and the symbol reel map are changed. Under all circumstances the reel stop map must comprise a number of memory locations with equals the number P+1 of symbols times the number n of possible stop positions per symbol. The symbol reel map must always comprise P+1 locations for P symbols. The mapping index array must have the same number of memory locations at the maximum as the reel stop map has, which is the case when operating the machine as a multiple stop gaming machine.
To make it possible for the combined gaming machine to operate according to any of said individual gaming machines the reel stop map must have memory locations for all possible physical stop positions, the number of symbols must be maintained under all circumstances and all symbols must have identical circumferential dimensions under all circumstances. Since the same software routine is used for several reels, the number of symbols for all reels must be identical. In addition, a random number generator must be designed to have a number range which equals the number of allowed stop positions. Therefore, for any change of the number of allowed stop positions the random number generator must be changed too and must be calibrated again, which is very time consuming and costly.
With the combined gaming machine using said one standard software routine, although the number of stop positions associated with each symbol on a reel could be any number, said number is considered to be rather small in practice in view of the requirement of reducing costs mentioned in the document, where a greater number of stop positions would increase the hardware and the complexity of mapping schemes for said one standard software routine. As a result said combined gaming machine is not suitable for having a reel stopped with a very high price paying symbol opposite a winning line with a very small probability.
EP-A-0338743 discloses, in its prior art part, a multiple stop gaming machine having two reel stops located very close together for certain symbols on the reels and one stop for other symbols. The symbols having two reel stops will have twice the probability of being stopped in a winning position, thus effectively decreasing the odds that a symbol with only one reel stop will appear in the winning positing. It is not substantiated what is meant by xe2x80x9cvery close togetherxe2x80x9d, how many reel stops are associated with each symbol field where the reel is allowed to stop or not, and how a distribution of allowed stop positions among unallowed stop positions must be.
It is an object of the invention to provide a multiple stop gaming machine which does not have said drawbacks.
To this end, the invention provides a gaming machine comprising a reel of which a circumferential surface is divided in a number of fields which each bear a symbol from several symbols, which may include a blank, drive means for rotating the reel, memory means for storing data representing allowed rotational stop positions of the reel where the reel is allowed to stop, the number of allowed stop positions being greater than said number of fields, random number generator means for randomly generating an address of a location of said memory means containing data representing an allowed stop position and stop means for controlling the drive means to stop rotation of the reel opposite a winning line at a rotational stop position which corresponds to said randomly generated memory means address, wherein adjacent rotational stop positions are less than 0,1xc2x0 apart from each other and for each field all allowed stop positions are located within an arc of 2xc2x0.
The stepping motor can provide a very great number, which number may be over 10.000, of rotational stop positions of the reel. By allowing only those stop positions to actually stop the reel which are difficult to distinguish with respect to the winning line by the naked eye, if opposite the associated field at stand still of the reel, the gaming machine appears to the player as a standard gaming machine or virtual reel gaming machine but with the provision of showing few symbols with a much smaller chance for higher prices.